Custom field types "Text" and "Text (Multiple)"

Hi,

when creating custom fields in a translation memory in Trados Studio 2021 (16.0.1.2917) the drop down list offers the types "Text", "Text (Multiple)", "List", and "List (Multiple)", among others. When exporting to TMX the text fields, for example, it results in "X-SingleString" and "X-MultipleString" note attribute values. What is the difference between these two types (and between "List" and "List (Multiple)")? Couldn't find out in the doc and by testing either.

Many thanks in advance

Detlef